This proposal is aimed at identifying and characterizing genes that regulate beta-amyloid precursor protein (APP) metabolism. Abnormal APP metabolism is a central event in Alzheimer's disease (AD). Specifically, proteolytic processing of APP to generate the amyloidogenic Beta-amyloid (ABeta) peptide is a fundamental process in AD pathogenesis. How this APP metabolism is regulated is not fully understood and a complete understanding could yield promising therapeutic avenues and insight into the genetic basis of AD. To identify regulators of APP metabolism, in the first aim we describe a focused genetic screen that combines monitoring some of the products of APP metabolism and RNAi-mediated silencing of specific human genes in a human neuronal cell line. We have previously demonstrated the successful development and validation of this approach and in this resubmission demonstrate successful identification of novel APP metabolism regulators utilizing this novel approach. In the second aim, we describe experiments aimed at determining if putative regulators modulate APP metabolism in a Drosophila model of AD. In this resubmission, we demonstrate using this model that our novel regulators do indeed regulate APP metabolism in vivo. In the third aim we describe how putative regulatory genes will be characterized in cell lines and primary neurons to determine the mechanism of APP metabolism regulation. Finally in the forth aim, we propose to determine the effects the regulatory gene on AD pathology using a transgenic mouse model of AD. Identified regulatory genes may be genetic risk factors for AD and should be considered high priority AD susceptibility genes because they regulate APP processing. Indeed, with our collaborators we have demonstrated that one of the novel regulators we recently identified contains polymorphisms that significantly increase AD risk. Our successful identification of novel APP metabolism regulators and our planned characterization of the mechanism of regulation is important to increasing our understanding of AD pathogenesis and may illuminate new avenues for therapeutic intervention. PUBLIC HEALTH RELEVANCE: Abnormal accumulation of a small protein in the brain's memory center seems to be the cause of Alzheimer's disease. Here we propose to identify the defects that are responsible for this abnormal accumulation. If we can accomplish this we may find new ways to treat Alzheimer's disease.